The present invention concerns a method for manufacturing a diorganopolysiloxane in which a polymerizable functional group is present at one end. More specifically, the present invention concerns a method for manufacturing, by a nonequilibrium polymerization process, a diorganopolysiloxane in which a polymerizable functional group is present as at least one of the ends and in which an arbitrary group is present as the other end.
It is a well-established fact in the present technical field that a cyclic trisiloxane can be opened and polymerized using an alkali metal catalyst. There is a compound in which the objective polymer is synthesized by nonequilibrium polymerization in the presence of a lithium catalyst, a so-called "living polymerization". J. Saam et al. note, in Macromolecules, Vol. 3, No. 1, p. 1 (1970), that if hexamethylcyclotrisiloxane is opened using butyllithium and if the polymerization is terminated by a vinylchlorosilane treatment, a diorganopolysiloxane in which a vinyl group is present at one end is obtained. Japanese Kokai Patent No. Sho 59(1984)-78236 notes a method for manufacturing diorganopolysiloxane according to comparable procedures. Such functional group-introducing techniques are commonly referred to as the "terminating method".
If the aforementioned conventional techniques are implemented, however, an endcapping reaction is induced when a high-molecular-weight product has been produced; therefore, there is no guarantee for completing said functional group-introducing reaction. Since no functional group is present at the molecule chain end (i.e., molecule head) at the beginning of polymerization, only monofunctional diorganopolysiloxanes are obtained in these techniques.
The present inventors compiled exhaustive research to alleviate the aforementioned problems inherent in said terminating methods. Thus, the present invention has been completed. The foremost objective of the present invention is to provide a method for manufacturing an organopolysiloxane in which a polymerizable functional group is assuredly introduced to at least the molecule chain end at the beginning of polymerization, i.e., molecule head.